Any time you create a wound in the skin like a body piercing, you run the risk of developing an infection. The risk increases if the equipment used to create the opening isn't scrupulously cleaned and sterilised between uses.
If the bump around a body piercing produces pain, swelling, oozing or a foul odour, you may have an infection. The risk increases if the symptoms persist or if the redness spreads of redness or turns dark red or purple and you develop a fever. You need antibiotics in addition to draining by your doctor to treat an infection. Sending the fluid for evaluation for the type of bacteria it contains is very important if the infection doesn't improve. A culture and sensitivity of the fluid determines the bacteria present as well as which antibiotics can effectively treat it.
A reddened bump doesn't always mean infection. In some cases, inflammation can develop at the site from irritation from the piercing rather than infection. With inflammation, the redness is usually localised, improves with time, doesn't spread and doesn't have a foul smell. Draining an inflamed bump won't help at all, since it doesn't contain infected material. Injecting the bump with cortisone often helps reduce inflammation, although you might need more than one treatment, depending on the size of the inflamed area.
Trying to drain an infected site yourself could make an infection much worse, especially if you use a contaminated tool and introduce even more bacteria into the wound. A serious infection that enters the blood stream can be fatal. Let your doctor determine whether a bump that develops at the site of a body piercing needs draining. Only a medical professional should perform this procedure.